Question
If $P=\left|\begin{array}{ll}2 & 9 \\ 5 & 7\end{array}\right|$ and $Q=\left|\begin{array}{ll}7 & 3 \\ 4 & 1\end{array}\right|$, find $2 P+3 Q$

Answer

$\begin{array}{l}=\left|\begin{array}{ll}2 & 9 \\ 5 & 7\end{array}\right|_{2 \times 2}, Q=\left|\begin{array}{ll}7 & 3 \\ 4 & 1\end{array}\right|_{2 \times 2}\end{array}  $
$ 2 P+3 Q=\left|\begin{array}{cc}4 & 18 \\ 10 & 14\end{array}\right|+\left|\begin{array}{cc}21 & 9 \\ 12 & 3\end{array}\right| $
$ =\left|\begin{array}{cc}4+21 & 18+9 \\ 10+12 & 14+3\end{array}\right|$
$=\left|\begin{array}{cc}25 & 27 \\ 22 & 17\end{array}\right|_{2 \times 2}$

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